PLZ HELP THIS IS FOR 2sixWEEKS Why do most roller coasters start by slowly taking the roller coaster carts up a very tall hill?

Each time they race up a hill, they gain more potential energy (by rising higher in the air), but they compensate for it by losing some kinetic energy too (by slowing down). That's why rollercoaster cars always go slower in the higher bits of a ride and faster in the lower bits.

Is a  vector quantity  that refers to "the rate at which an object changes its position." imagine a person moving rapidly - one step forward and one step back - always returning to the original starting position. while this might result in a frenzy of activity, it would result in a zero velocity. because the person always returns to the original position, the motion would never result in a change in position. since velocity is defined as the rate at which the position changes, this motion results in zero velocity. if a person in motion wishes to maximize their velocity, then that person must make every effort to maximize the amount that they are displaced from their original position. every step must go into moving that person further from where he or she started. for certain, the person should never change directions and begin to return to the starting position.

This did i unseated, sorry